Kim
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VK Commodore Engine Info
Black/Blue Motor Differences – General:
As far as the carbie motors go the main difference is the black head has better porting and different underhead shaped valves. Later VH blue motors and black carby motors also had a air pump which blows air into the exhaust system to afterburn the fuel left in the exhaust after combustion..
The blue motor has marginally better pistons. Also it has electronic dizzy which is reportedly more reliable than the VK carbed engine's Electronic Spark Timing setup..
The injected black motor has a higher lift cam than the carb engines, and also does not have the air pump system and has the electronic dizzy. Also the cam timing is retarded about 5 degrees to improve pollution but at the cost of some lower rpm torque. (Note that the carb engines' cams were also retarded for the same reasons (5.5 degrees on the VH engine, IIRC.
The piston design on both motors was changed from the red motor to get lighter pistons and on the blue motor are not too bad but on the black motor they crack up all the time. If rebuilding don't use GMH pistons get decent aftermarket ones.
Blue Dizzy on a Black Motor
1) Make sure that you also get the blue HEI dizzy as you will need to use that, due to the vk running an EST computer for the timing (doesnt have vacuum advance).
2) Replace the thermostat housing of the VK (with the temperature electronic sensor) with the VH housing (with the thermal vacuum switch), not necessary but recommended. The TVS supplies manifold vacuum to the vacuum advance canister when the engine overheats at idle, to help cool the engine down. In normal conditions, the TVS supplies ported vacuum to the dizzy's vac advance canister.
3) For wiring the power for the dizzy, The EST system switches the 12V- side of the coil, and the 12V+ side of the coil is connected to ignition - the pink power wire is on the same circuit as the choke, and idle shutoff solenoid. The VH HEI module will have a green wire to switch the negative side of the coil.
All you do is pull out the EST dizzy, and drop in a blue HEI dizzy. The pink wire stays connected to the + side of the coil, and the 2 wires from the HEI one hook onto the coil too. It's as easy as that. There is a brown wire in the VK that hooks onto the coil neg terminal for the tacho.
The VK and the HEI use the same coil, leads, cap and rotor.
VK Substitute Carburetter (Black and Blue Motor)
The most common cause of engine troubles with the 202 motors was the Varajet carbi. Whilst a reasonable proposition once new, now most examples are worn, hard to tune, and generally work to well below their potential. A cheap substitue for the varajet is a Weber (34ADM) off of the XE/F falcons. They cost around $40 dollars (plus adaption plate) and are easily fitted to these motors with only the accelerator cable mount needing to be modified. They not only provide greater horse power but also increase your fuel effeciency. I would like to see evidence of this on paper - if someone does the mod with before and after dynos, that would be good. (N/B: With the black motor in the VK the secondary throttle sensor must be disconected and the computer (EST) must be reset.
Questions, and some modified answers...
Q. Will the VK trimatic/flexplate hook up to the blue without alteration?
A. Blue and black crankshafts have the same bolt hole spacings and sizes, so either flywheel/flexplate will bolt to either.
Q. Will the black motor inlet/exhaust manifolds hook up to the blue?
A. Yes.
Q. What is the carby on the black motor (I haven't picked the car up yet) and is it a two barrel?
A. The Carby on the Black/Blue motor is a 2-barrel Rochester Varajet-II
Q. Can I run a 350 holley in it's place?
A. A GOOD CONDITION 350 holley CAN run really well on the stock 202, and can sometimes give better economy than what it's replacing (with a rejetting if it came off a different sized engine.). If you run a Holley you need to know that there is a micro switch on the Varijet that alters your ignition timing once you reach a certain rev range. One way to get around this is to rip the EST out and install that blue motor dizzy.
The blue motor has basically the same carbie though {no micro switch, just remember that if you use it}.
Q. Is there anything else I should do? (Looks like a question for hotting up a VK 6 cyl, so this was the opinion of the author, and definitely not mine...)
A. Pacemaker Extractors, 2.5 inch Mandrel Bent Lukey System, 35/75 or similar cam, re-graphed dizzy with new points, straight cut timing gears if you like noise or just a decent angle cut alloy gear set.
Hot 202 if you build them to last. ACL HQ race pistons, 35/72 solid cam and lifters, roller rockers, balanced/blueprinted bottom end, ARP rod bolts-a must, JP high volume oil pump, lightened flywheel, Stage 3 Yella Terra 12 port with an extra 30 thou shaved off it,20 thou off block deck, blue motor electronic ignition,4 barrel manifold and 600 Holley four barrel, let me know if you want any more info.
Q. The question here is, for this sort of motor will I need any porting do you think?
A. Port work-never hurts, depends on your budget, but with a cam profile of 25/65 don’t go too silly, just a bit of a cleanup would probably do.
Q. Will the 12 port head flow well enough with the standard sized valves?
A. Standard valves would be ok. All depends on your budget again.
Q. Is the lift within range of a standard hydraulic lifter/standard rocker combo for this motor?
A. Standard rocker gear would be fine, the only reason I had roller rockers was because with solid cams you need to be able to adjust valve clearances, bolt down and leave them. 202 gear is no good for solids, fine for hydraulicswith up to 0.450" valve lift on either the intake or exhaust.
Q. Is there any advantage in using a black head on a blue motor?
A. Yes, the black head flows more CFM from the above modifications.
Black/Blue Motor Differences – General:
As far as the carbie motors go the main difference is the black head has better porting and different underhead shaped valves. Later VH blue motors and black carby motors also had a air pump which blows air into the exhaust system to afterburn the fuel left in the exhaust after combustion..
The blue motor has marginally better pistons. Also it has electronic dizzy which is reportedly more reliable than the VK carbed engine's Electronic Spark Timing setup..
The injected black motor has a higher lift cam than the carb engines, and also does not have the air pump system and has the electronic dizzy. Also the cam timing is retarded about 5 degrees to improve pollution but at the cost of some lower rpm torque. (Note that the carb engines' cams were also retarded for the same reasons (5.5 degrees on the VH engine, IIRC.
The piston design on both motors was changed from the red motor to get lighter pistons and on the blue motor are not too bad but on the black motor they crack up all the time. If rebuilding don't use GMH pistons get decent aftermarket ones.
Blue Dizzy on a Black Motor
1) Make sure that you also get the blue HEI dizzy as you will need to use that, due to the vk running an EST computer for the timing (doesnt have vacuum advance).
2) Replace the thermostat housing of the VK (with the temperature electronic sensor) with the VH housing (with the thermal vacuum switch), not necessary but recommended. The TVS supplies manifold vacuum to the vacuum advance canister when the engine overheats at idle, to help cool the engine down. In normal conditions, the TVS supplies ported vacuum to the dizzy's vac advance canister.
3) For wiring the power for the dizzy, The EST system switches the 12V- side of the coil, and the 12V+ side of the coil is connected to ignition - the pink power wire is on the same circuit as the choke, and idle shutoff solenoid. The VH HEI module will have a green wire to switch the negative side of the coil.
All you do is pull out the EST dizzy, and drop in a blue HEI dizzy. The pink wire stays connected to the + side of the coil, and the 2 wires from the HEI one hook onto the coil too. It's as easy as that. There is a brown wire in the VK that hooks onto the coil neg terminal for the tacho.
The VK and the HEI use the same coil, leads, cap and rotor.
VK Substitute Carburetter (Black and Blue Motor)
The most common cause of engine troubles with the 202 motors was the Varajet carbi. Whilst a reasonable proposition once new, now most examples are worn, hard to tune, and generally work to well below their potential. A cheap substitue for the varajet is a Weber (34ADM) off of the XE/F falcons. They cost around $40 dollars (plus adaption plate) and are easily fitted to these motors with only the accelerator cable mount needing to be modified. They not only provide greater horse power but also increase your fuel effeciency. I would like to see evidence of this on paper - if someone does the mod with before and after dynos, that would be good. (N/B: With the black motor in the VK the secondary throttle sensor must be disconected and the computer (EST) must be reset.
Questions, and some modified answers...
Q. Will the VK trimatic/flexplate hook up to the blue without alteration?
A. Blue and black crankshafts have the same bolt hole spacings and sizes, so either flywheel/flexplate will bolt to either.
Q. Will the black motor inlet/exhaust manifolds hook up to the blue?
A. Yes.
Q. What is the carby on the black motor (I haven't picked the car up yet) and is it a two barrel?
A. The Carby on the Black/Blue motor is a 2-barrel Rochester Varajet-II
Q. Can I run a 350 holley in it's place?
A. A GOOD CONDITION 350 holley CAN run really well on the stock 202, and can sometimes give better economy than what it's replacing (with a rejetting if it came off a different sized engine.). If you run a Holley you need to know that there is a micro switch on the Varijet that alters your ignition timing once you reach a certain rev range. One way to get around this is to rip the EST out and install that blue motor dizzy.
The blue motor has basically the same carbie though {no micro switch, just remember that if you use it}.
Q. Is there anything else I should do? (Looks like a question for hotting up a VK 6 cyl, so this was the opinion of the author, and definitely not mine...)
A. Pacemaker Extractors, 2.5 inch Mandrel Bent Lukey System, 35/75 or similar cam, re-graphed dizzy with new points, straight cut timing gears if you like noise or just a decent angle cut alloy gear set.
Hot 202 if you build them to last. ACL HQ race pistons, 35/72 solid cam and lifters, roller rockers, balanced/blueprinted bottom end, ARP rod bolts-a must, JP high volume oil pump, lightened flywheel, Stage 3 Yella Terra 12 port with an extra 30 thou shaved off it,20 thou off block deck, blue motor electronic ignition,4 barrel manifold and 600 Holley four barrel, let me know if you want any more info.
Q. The question here is, for this sort of motor will I need any porting do you think?
A. Port work-never hurts, depends on your budget, but with a cam profile of 25/65 don’t go too silly, just a bit of a cleanup would probably do.
Q. Will the 12 port head flow well enough with the standard sized valves?
A. Standard valves would be ok. All depends on your budget again.
Q. Is the lift within range of a standard hydraulic lifter/standard rocker combo for this motor?
A. Standard rocker gear would be fine, the only reason I had roller rockers was because with solid cams you need to be able to adjust valve clearances, bolt down and leave them. 202 gear is no good for solids, fine for hydraulicswith up to 0.450" valve lift on either the intake or exhaust.
Q. Is there any advantage in using a black head on a blue motor?
A. Yes, the black head flows more CFM from the above modifications.
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